Axial flow or rotary combine harvesters are well known and manufactured by different companies. Generally the harvester comprises a combine rotor having a generally cylindrical body defining an outer rotor surface and mounted for rotation about a longitudinal axis of the body; a generally cylindrical concave assembly in which the rotor is mounted for rotation such that the rotor is substantially surrounded by a plurality of concave elements facing inwardly and arranged to cooperate with the outer rotor surface for effecting a threshing and separating action on the crop material passing through a generally cylindrical area between the rotor and the concave assembly; an impeller feed section at a forward end of the rotor and rotatable therewith for feeding the crop material rearwardly into the cylindrical area; a generally frusto-conical housing portion surrounding the impeller feed section and converging inwardly and rearwardly from a front feed mouth to the concave assembly such that rotation of the impeller feed section within the housing portion causes a rearward flow of the crop material from the mouth to the cylindrical area; and a feeder housing for feeding the crop material from a header into the open mouth.
The impeller feed section includes a mounting hub at a forward end of the rotor; a plurality of impeller blades, known colloquially as elephant ears, arranged at spaced positions around the axis so as to extend generally longitudinally of the rotor and curved to cause an air flow rearwardly as the blade portion rotates about the axis; where each impeller blade includes an inner mounting portion connected to the mounting hub and an outwardly extending blade portion. Each blade portion defines a forward blade edge and an outer blade edge, with the forward blade edges of the blades lying substantially in an imaginary common front radial plane of the impeller section at the front feed mouth and the outer blade edges lying substantially in an imaginary frusto-conical surface just inside the frusto-conical housing portion.
It is well known and an ongoing concern that this arrangement has a considerable difficulty in effecting the necessary feeding action in some crop conditions. Extensive efforts have been applied to overcoming this problem including particularly changes to the front wear bar which is attached along the forward edges of the blades. Up till now little improvement has been achieved.